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Application Notes

HOLD Function

The input value and alarms are frozen while the logic input is closed.

With logic input closed, a reset turns OFF both the relay outputs and the alarms latch.

Alarms

time

AL1 + Hy1

AL2 + Hy2

AL2

AL1

alarm 1

alarm 2

(*)

For AL1 = reverse absolute alarm (low) with positive Hyst1, AL1 t = 1

(*) = OFF if disabled on power-up

For AL2 = direct absolute alarm (high) with negative Hyst2, AL2 t = 0

For AL1 = symmetrical Lo absolute alarm with Hyst1, AL1 t = 5

For AL1 = symmetrical Hi absolute alarm with Hyst1, AL1 t = 4

* Minimum hysteresis = 2 scale points

Normal absolute alarm Symmetrical absolute alarm

reverse

direct

AL1

AL1 + [ Hy1* ]

AL1 - [ Hy1* ]

time

For AL1 = Lo deviation alarm with negative Hyst 1, AL1 t = 3

For AL1 = Hi deviation alarm with negative Hyst 1, AL1 t = 2

For AL1 = Symmetrical Lo deviation alarm with Hyst 1, AL1 t = 7

For AL1 = Symmetrical Hi deviation alarm with Hyst 1, AL1 t = 6

time

SP+AL1

reverse

direct

SP+AL1

inverso

direct

time

Hy1

Deviation alarm Symmetrical deviation Alarm

SP-AL1

N.B.: For deviation alarms (At.n = deviation) with different reference quantities (Ar.n), which are set with different decimal points, the switch setpoint always refers

to scale points without considering decimal point.

ex.: if Ar.n = 0 (referred to IN1) and At.n = 6 (deviation referred to IN3) and IN1 with dP = 1, IN3 with dP = 2 AL1 = 200.0 IN3 = 10.00 dS.SP = 1, the alarm

setpoint is 300.0

Control actions

Proportional Action:

action in which contribution to output is proportional to deviation at input (deviation = difference between controlled

variable and setpoint).

Derivative Action:

action in which contribution to output is proportional to rate of variation input deviation.

Integral Action:

action in which contribution to output is proportional to integral of time of input deviation.

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